1. Field of the Invention
This invention relates in general to electromagnetic relays and more specifically to a relay that aids in diagnosing circuit faults.
2. Discussion of Related Art
Relays are well known in the electrical art. A relay is an electromechanical switch. It operates by using relatively low electric current flowing in a first circuit to switch or direct the flow of a relatively higher electric current in a second circuit or multiple subsequent circuits. The object is to allow the use of a small amount of power in the first circuit to control a much greater amount of power in the subsequent circuit or circuits. Within the relay, an electromagnet is energized by the first circuit to exert an attraction force on an iron armature held adjacent the electromagnet. The armature overcomes the drag of a spring to move a contact to complete or break the second circuit. The spring returns the armature, and the connected contact, back to an original position when the electromagnet is de-energized.
Relay casings are often opaque and difficult or impossible to remove without destroying the relay. In order to diagnose a fault in a circuit that incorporates a relay, the service technician must test the relay in question to see if it is causing the fault. This is typically performed by either removing the relay from the circuit and plugging it into some kind of testing circuit, or substituting another, known to be functioning, relay. If the relay is not to blame the technician must probe each circuit individually for short and open circuits in a long and cumbersome process.
Some examples of prior art patents directed toward relay testing illustrate the lack of efficient and inexpensive field-testing available for relay circuits. A relatively large and complex relay tester for testing enclosed relays after a cover is affixed is set forth in U.S. Pat. No. 4,311,961. A stand has a jig for receiving a relay. A probe is inserted through an opening in a base of the relay into engagement with the movable contact of the relay. A microprocessor unit measures the electrical contact breaking force and probe displacement to determine whether contact travel is within set limits. U.S. Pat. No. 4,006,538 discloses an educational kit that allows a student to test relay control circuits and observe the operation of relay switches. Examples of devices that allow a kind of visual check of relay operation include U.S. Pat. No. 4,254,316. Transparent viewing members in a housing for contact modules receive reflected light indicating normal contact conditions. In U.S. Pat. No. 3,668,578, a transparent cover encloses the armature and contact assemblies of a relay to seal the elements from an outer environment. A separate, insulative cover encloses the electromagnet assembly.
Accordingly, it is an object of this invention to provide a relay for use in diagnosing faults in a relay circuit.
Another object of the invention is to make circuit elements of the relay easily accessible to a tester.
A further object of the invention is to enable movable physical components of the diagnostic relay to be observed and evaluated.
In carrying out this invention in the illustrative embodiment thereof, a diagnostic relay has holes or apertures extending through a top wall of its cover or casing. Upright contacts are used to extend the height of relay plugs or prongs through the casing to just under the apertures. This allows easy testing of each circuit in the relay. The service technician temporarily substitutes the diagnostic relay for the relay in the circuit. By temporarily replacing a particular relay in a circuit with the present invention, the service technician can electrically probe the circuits to find the fault by inserting leads of a multimeter through the apertures in the casing to engage the contacts. If the casing is opaque, markings on the casing may be used to identify the circuits. If the casing is transparent or clear, the operation of an armature assembly of the relay may be visually checked. The clear casing allows the technician to see if the armature assembly is operating properly. If the armature assembly does operate correctly and the circuits function as designed, then the problem is solved because the original relay was at fault. If the armature assembly does not operate properly, then the technician, using a schematic and the multimeter, can quickly check each circuit for expected voltage values and continuity, while keeping the whole system intact.